Known methods of biological tissue repair include sutures, staples and clips, sealants, and adhesives. Sutures are inexpensive, reliable, readily available and can be used on many types of lacerations and incisions. However, the use of sutures has many drawbacks. Sutures are intrusive in that they require puncturing of the tissue. Also, sutures require technical skill for their application. Sutures must be placed very precisely in order to properly align the tissue. Often the tissue must be manually realigned before each pass of the suture's needle. Imprecise placement of a suture may necessitate its removal and replacement; as a result, delicate tissues may be damaged. Sutures frequently must be removed postoperatively. Not only is this also time-consuming, but children often require either restraint, sedation, or additional exposure to general anesthetics. Sutures can also produce foreign body reactions and act as a nidus for infection. Finally, sutures pose the risk of needle-stick injury and transmissible infections for operating room personnel.
Staples or clips are preferred over sutures, for example, in minimally invasive endoscopic applications. Staples and clips require less time to apply than sutures, are available in different materials to suit different applications, and generally achieve uniform results. However, staples and clips are not easily adapted to different tissue dimensions and maintaining precision of alignment of the tissue is difficult because of the relatively large force required for application. Further, none of these fasteners is capable of producing a watertight seal for the repair.
Sealants, including fibrin-, collagen-, synthetic polymer- and protein-based sealants, act as a physical barrier to fluid and air, and can be used to promote wound healing, tissue regeneration and clot formation. However, sealants are generally time-consuming to prepare and apply. Also, with fibrin-based sealants, there is a risk of blood-borne viral disease transmission. Further, sealants cannot be used in high-tension areas.
Adhesives, for example, cyanoacrylate glues, have the advantage that they are generally easy to dispense. However, application of adhesives during the procedure can be cumbersome. Because of their liquid nature, these adhesives are difficult to precisely position on tissue and thus require adept and delicate application if precise positioning is desired. Cyanoacrylates also harden rapidly; therefore, the time available to the surgeon for proper tissue alignment is limited. Further, when cyanoacrylates dry, they become brittle. Thus, they cannot be used in areas of the body that have frequent movement. In addition, the currently available adhesives are not optimal for high-tension areas.
Laser tissue solders are a possible alternative for overcoming the problems associated with the above-mentioned techniques. Laser tissue soldering is a bonding technique in which a protein solder is applied to the surface of the tissue(s) to be joined and laser energy is used to bond the solder to the tissue surface(s). The term “light-activated adhesive” as used herein refers to laser tissue solders, as well as other now-known and later-developed adhesives which are used in combination with light energy.
The use of biodegradable polymer scaffolding in laser-solder tissue repairs has been shown to improve the success rate and consistency of such repairs. See, for example, McNally et al., U.S. Pat. No. 6,391,049. Laser-soldering techniques require light energy to be supplied to the repair site to activate the adhesive. Current laser soldering techniques are only suitable for a limited number of clinical applications. Accordingly, there is a need for improvements to currently-known light-activated techniques.